C8+ alpha-olefin dimers are attractive feedstocks for the production of waxes, lubricant additives, and basestocks. The dimeric products, which contain high levels of vinylidene unsaturation, are also desirable for use as reactive feedstocks for the production of surfactants, detergents, dispersants, and other additives.
Olefin dimerization reactions are typically carried out by contacting the desired alpha-olefin (typically decene) with a dimerization catalyst. Oligomerization of 1-decene tends to produce dimers, trimers, and tetramers, with 20, 30, and 40 carbon atoms in the molecule, respectively, such that the final reaction product has a fairly wide spectrum of molecular weight. There is, therefore, a significant need in developing catalysts which will dimerize C8+ alpha-olefins with high yield and high selectivity.
Although generally employed in the production of high molecular weight (>105 g/mol) polymers, certain metallocene and other single site catalysts have been used to produce lower molecular weight (<104 g/mol) polymers and oligomers. For example, U.S. Pat. No. 8,071,701 discloses at Table 4, PP17, PP22, and PP27, propylene polymerization of low activity at 75° C. using trityltetrakis(pentafluorophenyl)borate and a metal complex that is the combination of Zr(benzyl)4 and a ligand having the formula:

Other references of interest include: US 2014/163173; US 2014/275429; WO 2012/111777; WO 2012/111778; WO 2012/111779; WO 2012/111780; WO 2013/022108; JP 2013-053309A2; JP 2013-166735A2; JP 2013-166897 A; JP 2013-166898A; JP 2014-198744A; Topics in Catalysis (2014), 57(10-13), 918-922 (Completely Isospecific Polymerization of 1-Hexene Catalyzed by Hafnium(IV) Dichloro Complex Incorporating with an [OSSO]-type Bis(phenolate) Ligand, Nakata, Norio et al.); Macromolecules (2013), 46(17), 6758-6764 (Controlled Isospecific Polymerization of a-Olefins by Hafnium Complex Incorporating with a trans-Cyclooctanediyl-Bridged [OSSO]-Type Bis(phenolate) Ligand, Nakata, Norio, et al.).
According to the present invention, it has now been found that certain transition metal complexes of tetradentate [OSSO]-type bisphenolate ligands show unusual selectivity and conversion for the production of dimers of C8+ alpha-olefins.